[Spice-devel] libspice and save/restore/migration

[Gerd Hoffmann]

   Hi,

I want change the way save/restore works for the qxl device.


0.4 works this way:

savevm
   qxl:      call worker->save()
   worker:   call interface->set_save_data(data, size)
   qxl:      save data block.

loadvm
   qxl:      load data block.
   qxl:      call worker->load()
   worker:   call interface->get_save_data()

The data block passed back via set_save_data actually contains the local 
cursor.

Current spice devel tree still contrains these bits.  They don't work 
any more.  One of the reasons is the new surface code, which requires to 
save additional state (namely all the surfaces).  According to izik it 
was broken before too, dunno why (memslots maybe?).


Plan for unstable:

(1) Keep surface metadata in device memory, i.e. delay the release of
     QXL_SURFACE_CMD_CREATE command until the surface is destroyed.
(2) Keep the most recent QXL_CURSOR_SET command in device memory, i.e.
     delay the release until the next one comes in.
(3) qemu/qxl keeps track of the active surfaces and the cursor (the
     later is required anyway for local rendering).  Because of (1)+(2)
     it just needs to maintain pointers to the commands creating them.

savevm: qxl saves surface+cursor state (no help from libspice needed).

loadvm: qxl feeds libspice with the commands needed to restore state. 
This could be done using either the usual get_command() interface 
callbacks or with a new worker->loadvm_commands(cmdlist, count) call.

worker->{save,load} and interface->{get,set}_save_data() calls are not 
needed any more.


Comments?

cheers,
   Gerd